Solderless electrical connectors in which the conductor contact is reliably established by a simple assembling movement, have found widespread use because with such connectors, the particularly time consuming processes of stripping the insulation and soldering are eliminated. Such connectors are disclosed in U.S. Pat. Nos. 3,012,219; 3,573,713; and 3,656,088. In many cases, particularly where aluminum conductors are used, it has been found desirable to include a strain relief for the wires in the connector to prevent mechanical stresses on the wires from degrading the contact connection. To take full advantage of the increased assembly rates obtainable with such connectors the strain relief should be made effective by the same assembling movement which also establishes the electrical contact. Most of the known solderless connectors in which by a single assembling movement, the contact is established, as well as the conductor strain-relieved, employ two housing parts between which, upon assembling, the conductors are mechanically clamped, and contacted electrically. For example, in U.S. Pat. No. 3,576,518 a barb-like projection provided on one of the housing parts engages the insulation on the conductor. However, such projections may themselves cause conductor breakage, particularly with the use of fragile conductor materials like aluminum. Alternatively, the conductor has been clamped in a bend as in U.S. Pat. No. 3,936,128. With such clamping in a bend or loop of the conductor the contacting area can be strain relieved more effectively. However, as in the connector of U.S. Pat. No. 3,936,128, the deforming and clamping area of the strain relief has been provided at the wire entrance area spaced as far as possible from the contacting area, in order to be able to make the bend as large as possible and thus the strain relief as effective as possible. This, however, produces other disadvantages. Particularly with connectors in which the contacting area is protected against the influence of air by a filling material, movements of the conductors in the entrance area may loosen and work the filling material out of the housing. Furthermore, the electrical strength of the connector as a whole can be impaired if in the strain relief the insulation on the conductors is damaged or compressed upon clamping the conductors fast. Furthermore, it has been found that when connecting wires having fragile conductors, particularly aluminum, wire breaks may occur in the entrance area of the connector.